Tuesday, November 6, 2007 - 11:05 AM
153-5

Optimal Fertilizer Nitrogen Rates for Corn Production in the MidSouth.

Henry J. Mascagni Jr.1, Gary Breitenbeck2, Don Boquet3, and Ernie Clawson1. (1) Northeast Research Station, Louisiana State University Agricultural Center, Hwy 605 North, PO Box 438, St. Joseph, LA 71366, (2) Plant, Environment and Soil Sciences, Louisiana State University Agricultural Center, 104 Sturgis Hall, LSU - Baton Rouge, LA 70803, (3) Macon Ridge Research Station, Louisiana State University Agricultural Center, 212A Macon Ridge Road, Winnsboro, LA 71366

Fertilizer nitrogen (N) management is a key component for maximizing corn yield and profitability. Applying the optimal N rate goes a long way in enhancing fertilizer N use efficiency and, at the same time, minimizing environmental concerns related to nitrate pollution. In the mid-South corn/cotton rotations are becoming very popular, and measuring residual N is an important component for ensuring an efficient and environmental friendly N fertilizer management system. Fine-tuning fertilizer N management practices is particularly important because of the high cost of fertilizer N. Yield data from fertilizer N rate trials conducted from 1996 to 2007 on alluvial silt loam and clay soils and on loessial silt loam soils were summarized for determining optimal fertilizer N rates.  Optimal N rates ranged from 170 to 225 kg N ha-1 acre on alluvial silt loam and loessial silt loam and 110 to 270 kg N ha-1 on alluvial clay. Trials were also conducted evaluating timings of N fertilizer applications, including applications as late as tassel emergence. In these studies, end of the season residual N was estimated using basal stalk analyses. The N status of the plant, using remote sensing techniques and plant analyses, was determined and correlated with yield response. Yields for total N applied were similar regardless if applied in an early-season, single applications or split between early season and tassel emergence applications.

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